A Detailed Analytical Study of Hydrogen Reaction in a Novel Micromix Combustion System

2018 ◽  
Author(s):  
Ramzi Ben Abdallah ◽  
Vishal Sethi ◽  
Pierre Q. Gauthier ◽  
Andrew Martin Rolt ◽  
David Abbott
Keyword(s):  
Gas Turbine ◽  
Analytical Study ◽  
Fuel Injection ◽  
Numerical Models ◽  
Cross Flow ◽  
Diffusion Combustion ◽  
Thermal Boundary Conditions ◽  
Auto Ignition ◽  
Combustion Properties ◽  
Analytical Tools

Liquid hydrogen is considered a technically feasible fuel for all gas turbine applications including propulsion systems [1]. However, the exceptional combustion properties of hydrogen will make fundamental changes to gas turbine combustion systems essential. Micromixing, with a novel cross-flow fuel-injection feature and a large plurality of injection holes offers miniaturised diffusive combustion without the risk of auto-ignition or flashback. A detailed analytical study has been performed to explore combustion behaviour of hydrogen in the micro-diffusion combustor concept. The aims are to investigate a broad range of analytical tools and sensitivities related to hydrogen micromix combustion numerical modelling. Comparative studies based on a number of RANS and LES simulations were carried out to down-select suitable numerical models for species transport, turbulence, chemistry and thermochemistry. Simulation results were found to be particularly sensitive to the species diffusion effects. The study was then extended to identify proper thermal boundary conditions capable of replicating experimental work. A thorough discussion of the findings is provided. The study has generated a novel micromix-injector geometry promising to yield ultra-low NOx emissions. This paper sheds light on the difficulties encountered in modelling the combustion of a gaseous fuel (hydrogen) in a novel micro-diffusion combustion chamber and suggests effective approaches to overcome them. It also identifies additional benefits related to hydrogen as a fuel.

scholarly journals Conceptual Studies of a Fuel-Flexible Low-Swirl Combustion System for the Gas Turbine in Clean Coal Power Plants

2010 ◽  
Author(s):  
Kenneth O. Smith ◽  
Peter L. Therkelsen ◽  
David Littlejohn ◽  
Sy Ali ◽  
Robert K. Cheng
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Fuel Injection ◽  
Pollutant Emissions ◽  
Injection System ◽  
Combustion System ◽  
High Hydrogen ◽  
Swirl Combustion ◽  
Auto Ignition

This paper reports the results of preliminary analyses that show the feasibility of developing a fuel flexible (natural gas, syngas and high-hydrogen fuel) combustion system for IGCC gas turbines. Of particular interest is the use of Lawrence Berkeley National Laboratory’s DLN low swirl combustion technology as the basis for the IGCC turbine combustor. Conceptual designs of the combustion system and the requirements for the fuel handling and delivery circuits are discussed. The analyses show the feasibility of a multi-fuel, utility-sized, LSI-based, gas turbine engine. A conceptual design of the fuel injection system shows that dual parallel fuel circuits can provide range of gas turbine operation in a configuration consistent with low pollutant emissions. Additionally, several issues and challenges associated with the development of such a system, such as flashback and auto-ignition of the high-hydrogen fuels, are outlined.

Analysis of the Fuel Injection in Gas Turbine Premixing Systems by Experimental Correlations and Numerical Simulations

2006 ◽  
Author(s):  
G. Riccio ◽  
L. Schoepflin ◽  
P. Adami ◽  
F. Martelli
Keyword(s):  
Combustion Chamber ◽  
Gas Turbine ◽  
Fuel Injection ◽  
Cross Flow ◽  
Navier Stokes ◽  
Air Stream ◽  
Fuel Jet ◽  
Fuel Mixing ◽  
Gas Turbine Combustion ◽  
The Cross

This paper presents the aerodynamic study of two premixing systems for gas turbine combustion chamber based on detailed CFD 3-D simulations. The work was carried out with the aim to describe the aerodynamic and the mixing process in two different premixing system schemes, typical for DLE gas turbine combustion chamber. Results from different numerical tools (CFD 3-D and 0/1-D) for the estimation of the fuel jet pathway were compared. Both the premixer configurations analysed are related to the cross-flow injection scheme. The first one considers the fuel injection orthogonal to a low swirled air stream while the second one considers the fuel injection directly from hole rows drilled on the suction and pressure side of the swirler blades. The aerodynamic analysis of the premixing devices was focused on the fuel injection in terms of the jets pathway and air/fuel mixing in steady-state conditions. The aerodynamic investigations were performed by CFD 3-D “full Navier-Stokes” codes. Calculations were repeated, on the same mesh, by an in-house developed code (HybFlow) and by commercial codes also. Some previous experimental results were exploited to tune and validate the calculations. Results of the simulation were post-processed in order to allow a quantitative evaluation of the air/fuel mixing. Moreover the calculations were used to verify the accuracy of 0/1-D models, taken from the literature, for the estimation of the maximum penetration and the trajectory for the cross-flow of gaseous fuel jet, considering typical working conditions for gas turbine premixing system. Finally, preliminary considerations related to the fuel injection schemes and to the influence of the main injection conditions on the mixing were carried out.

Numerical Modelling of NOx Emissions and Flame Stabilization Mechanisms in Gas Turbine Burners Operating With Hydrogen and Hydrogen-Methane Blends

2020 ◽  
Author(s):  
Roberto Meloni ◽  
Matteo Cerutti ◽  
Alessandro Zucca ◽  
Maurizio Mazzoni
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Laminar Flame ◽  
Numerical Models ◽  
Flame Stabilization ◽  
Combustion Model ◽  
Pure Hydrogen ◽  
Nox Emissions ◽  
Paper Test ◽  
Annular Combustor

Abstract Main objective of this paper is to assess the capability of numerical models in predicting NOx emissions and flame stabilization mechanisms of a heavy-duty gas turbine burner when operated with hydrogen and hydrogen-methane blends. Effort focused on the selection of the proper input to pre-tabulated Flamelet Generation Manifold combustion model. A dedicated sensitivity to laminar flame speed formulation has been performed as well, since it primarily affects flame stabilization through the closure term of the progress variable transport equation. Available NOx emissions data from full scale annular combustor rig test with hydrogen-air mixtures are presented first in this paper: test results have been used to validate the numerical setup for the reference geometry. Then, the model has been used to predict NOx emissions of alternative geometries in case of pure hydrogen, allowing screening of viable options to reduce the scope of a dedicated test campaign. Concerning flame stabilization mechanisms, simulations have been carried out for a reference geometry first: data from dedicated tests have been used to specialize the tool. Results of modified geometries are shown, to explore the effect of different fuel injection patterns or internal channel modifications. Based on the analysis outcomes, a discussion is provided regarding advantages and drawbacks of each proposed solution, as well as the ability of modelling setup in catching varied flame stabilization mechanisms.

Swirl Effects on Distributed Combustion for Near Zero Emission Gas Turbine Application

2010 ◽  
Author(s):  
Ahmed E. E. Khalil ◽  
Vaibhav K. Arghode ◽  
Ashwani K. Gupta
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
High Heat ◽  
Spontaneous Ignition ◽  
Experimental Investigations ◽  
Diffusion Combustion ◽  
Swirl Intensity ◽  
Zero Emission ◽  
Colorless Distributed Combustion

Previous investigations of Colorless Distributed Combustion (CDC) demonstrated significant improvement in combustor’s performance. CDC is characterized by high recirculation of product gases, fast mixing, spontaneous ignition and distributed reaction, leading to avoidance of hotspots and much lower NOx emissions. In this investigation, CDC is sought with focus on tailored mixture preparation before ignition using swirl and achieving distributed combustion for developing near zero emission combustion under gas turbine combustion conditions. Numerical and experimental investigations have been performed on a cylindrical combustor. Different fuel injection and hot gases exit arrangements have been considered. Air was injected tangentially to produce vortical structure in the flow and produce high swirl intensity. Results obtained show ultra low NO emissions (∼3 PPM) at high heat release intensity of 36 MW/m3-atm at an equivalence ratio (Φ) of 0.6. The role of premixed and diffusion combustion is also examined.

Influence of Fuel Jet Momentum on Characteristics of a Reverse-Cross Flow Combustor

2017 ◽  
Author(s):  
Shreshtha Kumar Gupta ◽  
Vaibhav Arghode
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Direct Injection ◽  
Cross Flow ◽  
Pollutant Emissions ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Air Jet ◽  
Fuel Jet ◽  
Thermal Intensity

The current work is aimed towards development of high thermal intensity, low emission combustor for gas turbine engines. Employing discrete and direct injection of air and fuel in a combustion chamber and has been demonstrated to result in low pollutant emissions (NOx, CO, UHC). From our previous investigations, we found that the reverse-cross flow configuration, where air is injected from the exit end and fuel is injected in the cross flow of the injected air, results in favorable combustion and emission characteristics. Though the air jet is the dominant jet, the fuel jet can also influence the flow field, mixing and the combustion behavior inside the combustor, which is the subject of the current investigation. Here we investigate a high thermal intensity combustor relevant to gas turbine engines (at equivalence ratio of 0.8, the combustor operates at thermal intensity of 39 MW/m3-atm and heat load of 6.25 kW). Natural gas is used as the fuel and two different fuel injection diameters of 1 mm and 2 mm are investigated. This result in significantly higher (four times) fuel jet momentum from the smaller fuel injection port as compared to the larger port. From computational fluid dynamics (CFD) studies, it is observed that for the case with higher fuel jet momentum, the fuel jet deflects the air jet such that the flow pattern is significantly altered as compared to the case with lower fuel jet momentum. OH* chemiluminescece images show that the reaction zone location is significantly affected with high momentum fuel jet. NOx is reduced whereas CO is increased with higher momentum fuel jet.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

Predicting Flameholding for Hydrogen and Natural Gas Flames at Gas Turbine Premixer Conditions

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Elliot Sullivan-Lewis ◽  
Vincent McDonell
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Experimental Studies ◽  
Temperature Variations ◽  
Auto Ignition ◽  
Chamber Temperature ◽  
Transient Events ◽  
Significant Effort

Lean-premixed gas turbines are now common devices for low emissions stationary power generation. By creating a homogeneous mixture of fuel and air upstream of the combustion chamber, temperature variations are reduced within the combustor, which reduces emissions of nitrogen oxides. However, by premixing fuel and air, a potentially flammable mixture is established in a part of the engine not designed to contain a flame. If the flame propagates upstream from the combustor (flashback), significant engine damage can result. While significant effort has been put into developing flashback resistant combustors, these combustors are only capable of preventing flashback during steady operation of the engine. Transient events (e.g., auto-ignition within the premixer and pressure spikes during ignition) can trigger flashback that cannot be prevented with even the best combustor design. In these cases, preventing engine damage requires designing premixers that will not allow a flame to be sustained. Experimental studies were conducted to determine under what conditions premixed flames of hydrogen and natural gas can be anchored in a simulated gas turbine premixer. Tests have been conducted at pressures up to 9 atm, temperatures up to 750 K, and freestream velocities between 20 and 100 m/s. Flames were anchored in the wakes of features typical of premixer passageways, including cylinders, steps, and airfoils. The results of this study have been used to develop an engineering tool that predicts under what conditions a flame will anchor, and can be used for development of flame anchoring resistant gas turbine premixers.

Modeling of Gas Turbine Fuel Nozzle Spray

1997 ◽  
Vol 119 (1) ◽  
pp. 34-44 ◽  
Author(s):  
N. K. Rizk ◽  
J. S. Chin ◽  
M. K. Razdan
Keyword(s):  
Gas Turbine ◽  
Fuel Injection ◽  
Near Field ◽  
Continuous Phase ◽  
Liquid Sheet ◽  
Vapor Concentration ◽  
Fuel Vapor ◽  
Fuel Injector ◽  
Gas Temperature ◽  
Sheet Breakup

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the airassist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The presents investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.

Analysis of Water–Fuel Ratio Variation in a Gas Turbine With a Wet-Compressor System by Change in Fuel Composition

2017 ◽  
Vol 140 (5) ◽  
Author(s):  
Yonatan Cadavid ◽  
Andres Amell ◽  
Juan Alzate ◽  
Gerjan Bermejo ◽  
Gustavo A. Ebratt
Keyword(s):  
Gas Turbine ◽  
Burning Velocity ◽  
Thermal Power ◽  
Flame Temperature ◽  
Fuel Composition ◽  
Nox Formation ◽  
Gaseous Hydrocarbon ◽  
Power Generators ◽  
Fuel Ratio ◽  
Combustion Properties

The wet compressor (WC) has become a reliable way to reduce gas emissions and increase gas turbine efficiency. However, fuel source diversification in the short and medium terms presents a challenge for gas turbine operators to know how the WC will respond to changes in fuel composition. For this study, we assessed the operational data of two thermal power generators, with outputs of 610 MW and 300 MW, in Colombia. The purpose was to determine the maximum amount of water that can be added into a gas turbine with a WC system, as well as how the NOx/CO emissions vary due to changes in fuel composition. The combustion properties of different gaseous hydrocarbon mixtures at wet conditions did not vary significantly from each other—except for the laminar burning velocity. It was found that the fuel/air equivalence ratio in the turbine reduced with lower CH4 content in the fuel. Less water can be added to the turbine with leaner combustion; the water/fuel ratio was decreased over the range of 1.4–0.4 for the studied case. The limit is mainly due to a reduction in flame temperature and major risk of lean blowout (LBO) or dynamic instabilities. A hybrid reaction mechanism was created from GRI-MECH 3.0 and NGIII to model hydrocarbons up to C5 with NOx formation. The model was validated with experimental results published previously in literature. Finally, the effect of atmospheric water in the premixed combustion was analyzed and explained.

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